Muffler for vacuum-inducing motor

ABSTRACT

An air-filtering, sound-attenuating muffler. The muffler includes an attenuator box and a multi-layer muffler filler. The layers of the muffler filler are reticulated polyurethane foam of varying pore densities. Air is directed through the muffler from the least dense to the most dense layer.

United. States Patent 1191 Cannan et al.

[ MUFFLER FOR VACUUM-INDUCING MOTOR Inventors: Bernard M. Cannan, Downers Grove; Daniel A. DeBoo, West Chicago, both of Ill.

Servicemaster Industries Inc., Downers Grove, Ill.

Filed: Apr. 1, 1974 Appl. No.2 456,541

Assignee:

US. Cl. 181/50; 15/326; 55/276; 55/522; 55/DIG. 3; 181/71 Int. Cl FOlm 1/10 Field of Search 15/326, 347; 55/276, 476, 55/487, 522, DIG. 2, DIG. 3, DIG. 13, DIG. 16, DIG. 21, DIG. 30, DIG. 31; 181/36 A,

References Cited UNITED STATES PATENTS 2,586,935 2/1952 Gerson 55/DIG. 21

Primary Examiner-Joseph W. Hartary Assistant Examiner-John F. Gonzales Attorney, Agent, or Firm-Molinare, Allegretti, Newitt & Witcoff 5 7 ABSTRACT An air-filtering, sound-attenuating muffler. The muffler includes an attenuator box and a multi-layer muffler filler. The layers of the muffler filler are reticulated polyurethane foam of varying pore densities. Air is directed through the muffler from the least dense to the most dense layer.

11 Claims, 4 Drawing Figures PATENTEB MAY 1 3 I975 HHi'm-- 1 MUFFLER FOR VACUUM-INDUCING MOTOR BACKGROUND OF THE INVENTION Referring to FIGS. 1-4, a preferred embodiment of The present invention relates generally to a muffler, the pre invention Shown as a muffler, g r lly and more particularly to an air-filtering, soundattenuating muffler for use on a vacuum cleaning machine.

Such machines operate by means of a vacuuminducing motor. In many cases, this motor produces a highly objectionable shrill noise which is heard through the exhaust port of the motor.

Although the exhaust air is, for practical purposes, clean, it may contain dust and dirt particulate matter. In a sterile environment, such as a hospital, it is highly desirable that this very fine matter be filtered out of the air flow.

In addition, the flow of air through the exhaust port, especially in heavy duty or industrial cleaning machines, is direct and strong, and the force of the flow can adversely effect the sound attenuation capability of the muffler.

The exhaust air flow can also result in substantial air turbulence, such that dust and dirt particles in the vicinity of the cleaning machine become unsettled and airborne. This substantially reduces the effectiveness of the vacuum cleaning machine.

SUMMARY OF THE PRESENT INVENTION In a principal aspect, the present invention comprises an attenuator box which contains a muffler filler. The filler consists of a series of reticulated foam layers of varying pore densities (as defined below) which are arranged in order of increasing pore density. The flow of air from the vacuum motor, and thus the motor noise and dirt particles, is directed from an inlet of the attenuator box into the least dense filler layer. The air then passes and diffuses through the remaining denser layers and exits the muffler assembly through an outlet port.

It is thus an object of the present invention to provide a muffler assembly which substantially attenuates and absorbs the noise of a vacuum motor.

It is a further object of the present invention to provide a muffler which substantially filters dust and dirt particulate matter from the exhaust air of a vacuum motor.

It is also an object of the present invention to provide a muffler which substantially disrupts the flow of air from a vacuum motor thereby reducing the force of the air flow to a tolerable level.

Other objects and advantages of the present invention will become apparent in the following detailed description.

BRIEF DESCRIPTION OF THE DRAWING shown in FIG. 1;

FIG. 3 is an enlarged top view of the attenuator box shown in FIG. 2; and

FIG. 4 is an enlarged cross sectional view of the preferred embodiment shown in FIG. 1 taken along 4-4.

ignated 2. The muffler includes two basic components, i.e., an attenuator box 4 and a muffler tiller 6.

As shown in FIGS. 2, 3 and 4, the attenuator box 4 is rectangular and includes a substantially vertical partition 8 which divides the attenuator box 4, thereby defining an intake portion 10 and a muffler portion 12. A pair of substantially horizontal wall members l4, 16 are secured within the intake portion 10 to define an intake v chamber 18. The intake chamber 18 is connected to the vacuum-inducing motor of a vacuum cleaning machine (not shown) through an inlet port 20 in the upper wall member 14.

The intake chamber 18 is a significant feature of the present invention because it effectively and substantially disrupts the forceful flow of air from the vacuum motor. As this air passes through the inlet 20, it impinges upon the lower wall member 16, and thus, the uniform flow pattern is substantially destroyed. The air then continuously and randomly circulates within the intake chamber 18.

As shown, the wall members 14, 16 are recessed from the top and bottom surfaces 22, 24 of the attenuator box 4. This facilitates attachment of the muffler 2 to the vacuum cleaning machine.

The muffler portion 12 is adapted to receive the muffler tiller 6. The muffler portion 12 defines a cavity, generally designated 26, which directly communicates with the intake chamber 18 through a substantially horizontal slot 28 in the partition 8.

The muffler portion 12 also defines a pair of outlet ports 30, 32 in the top and bottom surfaces 22, 24, respectively, of the attenuator box 4. A pair of flanges 34, 36 extend peripherally about the outlet ports 30, 32, respectively. The flanges 34, 36 assist in maintaining the muffler filler 6 within the cavity 26.

The muffler tiller 6, shown in cross-section in FIG. 4, is a composite structure including a series of reticulated foam layers, generally designated 38. The layers 38 are 'open cell polyurethane foam of varying pore density. As used herein, the term pore density is defined as pores per linear inch. Such foam is presently available under the trade name Scotts Industrial Foam.

In this preferred embodiment of the present invention, the center layer 40 of the muffler tiller 6 is the least dense layer and the layers 42-56 are arranged in order of increasing pore density about the center layer 40. That is, the pore density of the layers 38 increases from the center layer 40 to the exterior layers 54, 56.

The preferred pore densities are given in the following table.

It should be noted that the center layer 40 is twice as thick as the other layers 42-56. This is the result of the process used in fabricating the muffler tiller 6. From 3 stock material, sheets of 10, 25, 65, 80 and 100 PPI are cut to appropriate dimensions and secured together by appropriate means, such as gluing or sewing. This block of material is then folded upon itself and the interface between the two layers of 10 PPI is glued or sewn to produce the muffler filler 6, as shown.

In operation, the flow of air from the vacuum motor, shown in FIG. 4 by an arrow 58, enters the intake chamber 18 through the inlet port 20. The flow 58 is substantially interrupted, as indicated above, and the air is directed through the slot 28 into the muffler portion 12 of the attenuator box 4.

More specifically, and-as shown in FIG. 4, the slot 28 substantially aligns with the center layer 40 of the muffler filler 6, and thus, the air passes directly into the center layer 40. The air then diffuses vertically upwards and downwards through the remaining, more dense layers 4256 and exits the muffler 2 through the outlets 30, 32. As such the muffler 2 includes air control means, generally designated 60, for directing the flow of air 58 directly into the center and least dense layer 40 of the muffler filler 6,.and then through the remaining, increasingly dense layers 42-56.

The muffler filler 6 of varying pore density reticulated foam layers 38 provides substantial sound attentuation, without substantial reflection or back pressure problems. The center layer 40, being of lowest pore density, presents only limited resistance to the flow of air through the slot 28, and the graduation of densities 30 about the center layer 40 permitsthe air to readily diffuse through the muffler filler 6. This substantially avoids the problem of air reflection back towards and through the slot 28.

On the other hand, the open pore surface area'incrementally increases as the layers 38 become more dense. Thus, the sound absorbing capability of the layers 38 incrementally increases from the center layer 40 to the exterior layers 54, 56. Each layer 42-56 also presents additional interference and resistance to the air flow 58, such that the flow of air through the outlet ports 30,

made without departing from the true scope and spirit of the present invention, as defined in the following claims. For example, the attenuator box 2 need not be box-shaped, and use of the term box should not be construed in the sense of a limitation.

What is claimed is:

1. An airfiltering, sound-attenuating muffler for a vacuum-inducing motor comprising, in combination:

an attenuator box having an inlet and an outlet, said inlet being in direct communication with said,

motor for receiving a flow of air from said motor, said attenuator box defining a muffler cavity;

a muffler filler within said muffler cavity, said muffler filler including a series of reticulated foam layers of varying pore densities, said layers being arranged in order of increasing pore density, a first layer having I the lowest pore density; and

air control means for directing said flow of air from said inlet into said first layer of said muffler material and through said series of layers and said outlet, whereby the noise produced by said motor and carried by said air is substantially absorbed and attenuated by said muffler.

2. A muffler as claimed in claim 1 wherein said attenuator box further defines an intake chamber in direct communication with said inlet, whereby said flow of air from said motor is substantially disrupted.

"3. A muffler as claimed in claim 2 wherein said air control means defines a slot, said'intake chamber directly communicating with said muffler cavity through said slot.

4. A muffler as claimed in claim 3 wherein said slbt substantially aligns with said first layer of said muffler filler.

5. A muffler as claimed in claim 1 wherein said reticulated foam layers are open cell polyurethene foam.

6. A muffler as claimed in claim 1 wherein said pore densities vary from 10 to 100 pores per linear inch.

7. An air-filtering, sound-attenuating muffler for vacuum-inducing motor comprising, in combination:

an attenuator box having inlet means and outlet means, said inlet means receiving a flow of air from said motor, said attenuator defining a muffler cava muffler filler within said muffler cavity, said muffler filler including a series of reticulated foam layers of varying pore densities, a central layer having the lowest pore density, a first outer layer and a second outer layer having the highest pore density, said first and second outer layers being in direct communication with said outlet means, said layers being arranged about said central layer in order of increasing pore densities; and

air control means for directing said flow of air from said inlet into said central layer, whereby said air passes through said muffler filler in two directions and exists said attenuator box through said outlet means.

8. A muffler as claimed in claim 7 wherein said air control means includes an air passageway between said 45 inlet and said muffler filler.

, 9. A muffler as claimed in claim 8 wherein said air passageway is a slot, said slot substantially aligning with said central layer.

10. A muffler as claimed in claim 7 wherein said reticulated foam layers are open cell polyurethane foam.

11. A muffler for a vacuum-inducing motor comprising, in combination:

an attenuator box having an inlet, said inlet being in direct communication with said motor for receiving a flow of air from said motor, said attenuator box defining a muffler cavity;

a muffler filler with said muffler cavity, said filler including a series of foam layers of varying pore densities, a first layer having the lowest pore density and a second layer having the greatest poredensity;

and

air control means for directing said flow of air from said inlet into and through said muffler filler from said first layer to said second layer, whereby the noise produced by said motor and carried by said air is substantially absorbed and attenuated by said muffler. 

1. An air-filtering, sound-attenuating muffler for a vacuuminducing motor comprising, in combination: an attenuator box having an inlet and an outlet, said inlet being in direct communication with said motor for receiving a flow of air from said motor, said attenuator box defining a muffler cavity; a muffler filler within said muffler cavity, said muffler filler including a series of reticulated foam layers of varying pore densities, said layers being arranged in order of increasing pore density, a first layer having the lowest pore density; and air control means for directing said flow of air from said inlet into said first layer of said muffler material and through said series of layers and said outlet, whereby the noise produced by said motor and carried by said air is substantially absorbed and attenuated by said muffler.
 2. A muffler as claimed in claim 1 wherein said attenuator box further defines an intake chamber in direct communication with said inlet, whereby said flow of air from said motor is substantially disrupted.
 3. A muffler as claimed in claim 2 wherein said air control means defines a slot, said intake chamber directly communicating with said muffler cavity through said slot.
 4. A muffler as claimed in claim 3 wherein said slot substantially aligns with said first layer of said muffler filler.
 5. A muffler as claimed in claim 1 wherein said reticulated foam layers are open cell polyurethene foam.
 6. A muffler as claimed in claim 1 wherein said pore densities vary from 10 to 100 pores per linear inch.
 7. An air-filtering, sound-attenuating muffler for vacuum-inducing motor comprising, in combination: an attenuator box having inlet means and outlet means, said inlet means receiving a flow of air from said motor, said attenuator defining a muffler cavity; a muffler filler within said muffler cavity, said muffler filler including a series of reticulated foam layers of varying pore densities, a central layer having the lowest pore density, a first outer layer and a second outer layer having the highest pore density, said first and second outer layers being in direct communication with said outlet means, said layers being arranged about said central layer in order of increasing pore densities; and air control means for directing said flow of air from said inlet into said central layer, whereby said air passes through said muffler filler in two directions and exists said attenuator box through said outlet means.
 8. A muffler as claimed in claim 7 wherein said air control means includes an air passageway between said inlet and said muffler filler.
 9. A muffler as claimed in claim 8 wherein said air passageway is a slot, said slot substantially aligning with said central layer.
 10. A muffler as claimed in claim 7 wherein said reticulated foam layers are open cell polyurethane foam.
 11. A muffler for a vacuum-inducing motor comprising, in combination: an attenuator box having an inlet, said inlet being in direct communication with said motor for receiving a flow of air from said motor, said attenuator box defining a muffler cavity; a muffler filler with said muffler cavity, said filler including a series of foam layers of varying pore densities, a first layer having the lowest pore density and a second layer having the greatest pore density; and air control means for directing said flow of air from said inlet into and through said muffler filler from said first layer to said second layer, whereby the noise produced by said motor and carried by said air is substantially absorbed and attenuated by said muffler. 